A few clarifications:
You have a B15 (00-06).The GTi-R uses an SR20DET, but it has a larger turbo and different head than the Bluebird and Avenir versions.
I seem to recall the 1.8's transmission being the same as the 2.0s (minus the LSD).
You'd need a new exhaust system for sure, even if it did bolt up, the restriction would kill your turbo. There are a few brands out there. Check our advertisers -
http://nicoclub.com/addirectory.shtml
I hope the shop knows what they're getting into. This isn't a drop-in and go swap. The GTi-R will require a different flywheel setup, among other things. Do a search for GTi-R swap and you'll be able to find all the differences.
The GA->SR parts guide doesn't quite fit what you're doing since you have a B15. You'll want to use 00-01 SE parts instead of SE-R parts, but I think most of the GXE stuff is actually the same as the SE.